Many communication networks include multiple access devices communicating with a hub device. Anomalies in a communication channel between an access device and the hub may induce signal distortions in the channel, thereby causing issues such as inter-symbol interference (ISI). Examples of such anomalies may include micro-reflections due to impedance discontinuities and the ingress of noise from external sources.
To compensate for anomalies, devices (e.g., transmitters and receivers) on the network may incorporate equalizers. For anomalies that are known and are static (e.g., do not change over time), equalizers with fixed parameters may be designed and utilized. For example, fixed equalizers may be inserted at amplifiers along a signal path to correct for amplitude tilt due to frequency dependent attenuation along the signal path (e.g., along a coaxial cable). Fixed equalizers, however, may be insufficient for mitigating dynamic anomalies that change over time, such as the ingress of noise through an unshielded signal path. Such anomalies may be induced, for example, by the momentary operation of a motor or transformer next to the signal path, or by an external transmitter outside of the communication system (e.g., cellular phone, wireless transmitter, etc.). To compensate for changing anomalies, adaptive equalizers may be used. Adaptive equalizers, as their name suggests adapt their characteristics according to changing distortions in the communication channel. Various algorithms may be used to determine the equalizers coefficients based on measured distortions in order to optimize signal transmission. The distortions are measured and the equalizer coefficients are calculated and updated in a sufficiently short amount of time in order to account for the changing environment.
While adaptive equalizers may improve signal transmission, not all distortions can be compensated for by using an adaptive equalizer. Thus, a need exists to be able to locate and correct the cause of dynamic distortions. However, finding the location of such distortions is problematic. For example, the source of the noise may not be generated by a device in the communication network (e.g., access device, splitter, etc.), and because the noise source may not always be present.